From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK
Date: Thu, 24 Jan 2019 09:43:47 +0000 [thread overview]
Message-ID: <9b4dab64-6a6b-a599-4676-bf891473ada7@c-s.fr> (raw)
In-Reply-To: <87y37ax3ru.fsf@concordia.ellerman.id.au>
On 01/24/2019 01:06 AM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> Le 12/01/2019 à 10:55, Christophe Leroy a écrit :
>>> The purpose of this serie is to activate CONFIG_THREAD_INFO_IN_TASK which
>>> moves the thread_info into task_struct.
>>>
>>> Moving thread_info into task_struct has the following advantages:
>>> - It protects thread_info from corruption in the case of stack
>>> overflows.
>>> - Its address is harder to determine if stack addresses are
>>> leaked, making a number of attacks more difficult.
>>
>> I ran null_syscall and context_switch benchmark selftests and the result
>> is surprising. There is slight degradation in context_switch and a
>> significant one on null_syscall:
>>
>> Without the serie:
>>
>> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
>> 55542
>> 55562
>> 55564
>> 55562
>> 55568
>> ...
>>
>> ~# ./null_syscall
>> 2546.71 ns 336.17 cycles
>>
>>
>> With the serie:
>>
>> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
>> 55138
>> 55142
>> 55152
>> 55144
>> 55142
>>
>> ~# ./null_syscall
>> 3479.54 ns 459.30 cycles
>>
>> So 0,8% less context switches per second and 37% more time for one syscall ?
>>
>> Any idea ?
>
> What platform is that on?
It is on the 8xx
>
> On 64-bit we have to turn one mtmsrd into two and that's obviously a
> slow down. But I don't see that you've done anything similar in 32-bit
> code.
>
> I assume it's patch 8 that causes the slow down?
I have not digged into it yet, but why patch 8 ?
I run null_syscall with perf, and I get the following. Can we conclude
on something with that ?
Without the serie:
# Overhead Samples Command Shared Object Symbol
# ........ ............ ............ .................
........................................
#
32.95% 46375 null_syscall [kernel.kallsyms] [k] DoSyscall
23.64% 33275 null_syscall [kernel.kallsyms] [k]
__task_pid_nr_ns
15.47% 21778 null_syscall libc-2.23.so [.]
__GI___getppid
8.92% 12556 null_syscall [kernel.kallsyms] [k]
__rcu_read_unlock
5.69% 8014 null_syscall [kernel.kallsyms] [k] sys_getppid
4.01% 5643 null_syscall [kernel.kallsyms] [k]
__rcu_read_lock
3.67% 5166 null_syscall [kernel.kallsyms] [k]
syscall_dotrace_cont
2.52% 3542 null_syscall null_syscall [.] main
With the serie:
30.04% 56337 null_syscall [kernel.kallsyms] [k] DoSyscall
13.89% 26060 null_syscall [kernel.kallsyms] [k]
__rcu_read_unlock
13.36% 25062 null_syscall libc-2.23.so [.]
__GI___getppid
12.73% 23872 null_syscall [kernel.kallsyms] [k]
__task_pid_nr_ns
11.21% 21033 null_syscall [kernel.kallsyms] [k] sys_getppid
8.24% 15457 null_syscall [kernel.kallsyms] [k]
syscall_dotrace_cont
4.38% 8217 null_syscall [kernel.kallsyms] [k]
ret_from_syscall
2.54% 4773 null_syscall null_syscall [.] main
Christophe
next prev parent reply other threads:[~2019-01-24 9:43 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-12 9:55 [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 01/10] powerpc/irq: use memblock functions returning virtual address Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 02/10] book3s/64: avoid circular header inclusion in mmu-hash.h Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 03/10] powerpc: Only use task_struct 'cpu' field on SMP Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 04/10] powerpc: Prepare for moving thread_info into task_struct Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 05/10] powerpc: Activate CONFIG_THREAD_INFO_IN_TASK Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 06/10] powerpc: regain entire stack space Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 07/10] powerpc: 'current_set' is now a table of task_struct pointers Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 08/10] powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 09/10] powerpc/64: Remove CURRENT_THREAD_INFO Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 10/10] powerpc: clean stack pointers naming Christophe Leroy
2019-01-19 10:23 ` [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK Michael Ellerman
2019-01-19 17:21 ` LEROY Christophe
2019-01-23 23:10 ` Michael Ellerman
2019-01-22 19:42 ` Christophe Leroy
2019-01-24 0:59 ` Michael Ellerman
2019-01-24 15:08 ` Christophe Leroy
2019-01-23 10:04 ` Christophe Leroy
2019-01-24 1:06 ` Michael Ellerman
2019-01-24 9:43 ` Christophe Leroy [this message]
2019-01-24 15:01 ` Christophe Leroy
2019-01-24 15:58 ` Christophe Leroy
2019-01-25 7:00 ` Gabriel Paubert
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